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Containment · HEPA Cleaning · Drywall Removal · Attic · Crawlspace · HVACProfessional mold remediation generally runs $10 to $25 per square foot of affected area, so a 100 sq ft basement wall is about $1,000 to $2,500 before anything is rebuilt. Price HVAC cleaning, clearance testing and new drywall separately, then check the mold limit in your policy—some cap it at $5,000 or $10,000 even when the water loss behind it is covered.
Reviewed 25 October 2026 · Written by Mantu Kumar
See the illustrated inspection guide · How the system works
Sources: U.S. EPA “Mold Cleanup in Your Home”, This Old House mold remediation cost guide, published insurer mold limits, and ReplaceCost 2026 planning ranges.
2026 planning ranges
Typical installed: $10–$25 per sq ft affected Most jobs $1,200–$3,750 Whole-house $10,000–$30,000
Diagram, part by part
The mold remediation drawing above has 9 numbered parts, from Fix the water source first to Mold limits in your policy. Each card below frames one of them, and after you run the calculator it shows what that part adds to your estimate.
Separate trade, not in this estimate
Mold returns if the water does. A leaking pipe, roof or window, condensation or a damp crawl space is fixed first, often by a plumber or roofer, before remediation starts.
What moves it: The cause of the moisture and how hard it is to reach.
On the quote: Ask who repairs the leak and make sure it is done before the walls are closed.
Plastic sheeting seals the work area and an air scrubber with a HEPA filter keeps it under negative pressure, so spores stay inside the containment instead of spreading through the house. Workers enter through a zippered door.
What moves it: The size of the area and how many rooms it touches.
On the quote: Check that containment and negative air are written into the scope.
Added when drywall must come out
Moldy drywall, carpet pad and insulation cannot be cleaned and must come out. Crews cut a foot or two beyond the visible growth, bag the material inside the containment and carry it out sealed.
What moves it: Affected area and how far the moisture spread inside the wall.
On the quote: Ask for photos of each cut and of the framing before cleaning.
Inside the removal line
Exposed framing and surfaces are HEPA vacuumed, cleaned and dried with dehumidifiers. Wood is replaced only when it is structurally damaged, so cleaning is the bulk of the work.
What moves it: Area, access and drying time.
On the quote: Ask how dryness is measured and what moisture reading is the target.
Before walls are closed, a visual inspection or air and surface sampling confirms the area is clean and dry. Using an independent assessor, not the remediation company, avoids a conflict of interest.
What moves it: Number of samples and the lab used.
On the quote: Ask who does the clearance test and get the report in writing.
Once cleared, insulation, drywall, finishing and paint go back. Rebuild is often done by a separate contractor and should be its own line on the estimate.
What moves it: Area removed and the finish level.
On the quote: Confirm the rebuild is priced, and by whom.
If the air handler or ducts ran while mold grew, the coil, blower and ducts are cleaned so spores are not blown back through the house.
What moves it: Whether only the unit or the full duct system is affected.
On the quote: Ask whether the HVAC system was inspected and what cleaning method is used.
+15% to +20%
Mold on attic roof sheathing or crawl space framing is slower to clean because crews work bent over in heat or tight spaces. Attic mold usually comes from poor ventilation or bath fans venting into the attic, which must be fixed too.
What moves it: Access height, area and ventilation fixes needed.
On the quote: Ask how the cause, such as attic ventilation or a vapor barrier, is being corrected.
Often capped by the policy
Many homeowners policies cover mold only when it results from a covered, sudden leak, and many cap mold remediation at a set amount. Mold from long-term seepage or humidity is usually excluded.
What moves it: Your policy wording and the cause of the moisture.
On the quote: Check the mold or fungi section of your policy and keep proof of when the leak started.
Surface clean or tear-out
Mold on hard, non-porous surfaces can often be cleaned in place. Mold in wet drywall, insulation or carpet has to come out. Most of the price difference between two quotes is how much material each one plans to remove, and whether rebuilding the wall is in the number at all.
The three close-ups below show what to check in the wall cavity, at the cut line and on the floor before you approve a scope. These close-ups are crops of the same AI-generated illustration.
The EPA notes that dead mold can still cause allergic reactions, so killing it is not enough—it has to be removed. A good quote lists the square feet of drywall and insulation coming out, not just an area to be “treated”.
Drywall is normally cut above the highest wet or moldy point found with a moisture meter, often at 2 or 4 feet to match sheet sizes. A cut that stops at the visible stain can leave wet material inside the wall.
Carpet pad and some flooring trap moisture and may have to go too. Nothing should be closed up until the remaining wood and concrete read dry, so ask who takes that reading and when.
Where the mold is matters as much as how much there is. Tight crawl spaces and attics slow the crew down and need more containment; HVAC systems need specialist cleaning; bathrooms are usually small, contained jobs.
| Location | Typical range | What drives the price |
|---|---|---|
| Bathroom | $500 – $1,000 | Usually surface growth from humidity; more if a hidden leak soaked the wall |
| Basement | $500 – $3,000 | Drywall and insulation removal along the lower wall, plus drying |
| Crawl space | $500 – $2,000 | Access height, vapor barrier replacement and joist cleaning |
| Attic | $1,000 – $4,000 | Roof sheathing area, insulation removal and ventilation fixes |
| HVAC system | $3,000 – $10,000 | Air handler, coil and ductwork cleaning; the system should not run while contaminated |
| Whole house | $10,000 – $30,000 | Long-hidden leaks, flooding or growth in several rooms and the HVAC |
At $10 to $25 per square foot, the size of the affected area sets the baseline. Measure the area of wall, ceiling or floor with growth or water damage, not the size of the room.
| Affected area | Remediation range |
|---|---|
| 50 sq ft | $500 – $1,250 |
| 100 sq ft | $1,000 – $2,500 |
| 200 sq ft | $2,000 – $5,000 |
| 500 sq ft | $5,000 – $12,500 |
| 1,000 sq ft | $10,000 – $25,000 |
Small jobs rarely come in below a minimum charge, because setting up containment and equipment takes the same time whether the patch is 20 or 60 square feet.
The industry reference for professional work is the ANSI/IICRC S520 standard for mold remediation. In practice a complete job follows the same order shown in the diagram above:
Be wary of a quote that only sprays or fogs a chemical over drywall without removing wet material. The EPA’s guidance is that the purpose of cleanup is to remove the mold, because dead mold can still cause reactions.
The EPA says that if the moldy area is less than about 10 square feet—roughly a 3 ft by 3 ft patch—you can usually handle it yourself, provided you fix the water problem and wear basic protection. Bring in a contractor experienced in mold cleanup when growth covers more than about 10 square feet, when there has been a lot of water damage, when the water was contaminated sewage, or when mold may be in the heating and cooling system. If you suspect the HVAC system is contaminated, the EPA advises not running it.
These are the calculator’s default inputs: 100 sq ft of affected basement wall, wet drywall and insulation removed, no HVAC work, an independent clearance check, rebuilding the wall, national labor, materials 15 years old and a $1,000 deductible.
| Line item | 2026 planning range |
|---|---|
| Containment, removal of wet drywall and insulation, HEPA cleaning and drying (100 sq ft) | $1,000 – $2,500 |
| Independent clearance check before the wall is closed | $300 – $800 |
| Rebuild: insulation, drywall, finishing and paint (100 sq ft) | $400 – $900 |
| Planning total | $1,700 – $4,200 |
The remediation line alone matches the published $10 to $25 per square foot. The leak repair that caused the mold is not included, and neither is replacing flooring.
The calculator's default mold remediation job, repriced for each of its six regions. At the national average it runs $1,700 – $4,200; South / Lower Midwest is the lowest at $1,479 – $3,654, and West Coast metro is the highest at $2,210 – $5,460, a gap of about $1,268 at the midpoint.
| Region | Planning range | Midpoint |
|---|---|---|
| National average | $1,700 – $4,200 | $2,950 |
| South / Lower Midwest | $1,479 – $3,654 | $2,566 |
| Mountain / Plains | $1,615 – $3,990 | $2,802 |
| Mid-Atlantic / Upper Midwest | $1,904 – $4,704 | $3,304 |
| Northeast metro | $2,142 – $5,292 | $3,717 |
| West Coast metro | $2,210 – $5,460 | $3,835 |
Every other input stays at its default and only “HVAC system” changes. The cheapest choice, Not affected, comes to $1,700 – $4,200; the most expensive, Clean air handler, coil and ductwork, comes to $6,700 – $14,200.
| Choice | Planning range | Midpoint vs default |
|---|---|---|
| Not affected (default) | $1,700 – $4,200 | — |
| Clean air handler / furnace and coil | $4,700 – $9,200 | +$4,000 |
| Clean air handler, coil and ductwork | $6,700 – $14,200 | +$7,500 |
Every other input stays at its default and only “Material condition” changes. The cheapest choice, Surface growth on wood or concrete (clean in place), comes to $1,050 – $2,675; the most expensive, Wet drywall or insulation must be removed, comes to $1,700 – $4,200.
| Choice | Planning range | Midpoint vs default |
|---|---|---|
| Surface growth on wood or concrete (clean in place) | $1,050 – $2,675 | −$1,088 |
| Wet drywall or insulation must be removed (default) | $1,700 – $4,200 | — |
Using the default job, a $1,000 deductible and a 30-year expected life. At 10 years old, about $983 is held back as depreciation; a replacement cost policy releases it after the work is finished, while an actual cash value policy keeps it.
| Age | Wear | First check | Held back |
|---|---|---|---|
| 2 years | 7% | $1,753 | $197 |
| 5 years | 17% | $1,458 | $492 |
| 10 years | 33% | $967 | $983 |
| 15 years | 50% | $475 | $1,475 |
| 20 years | 67% | $0 | $1,967 |
| 30 years | 80% | $0 | $2,360 |
Mold quotes are easiest to compare when the scope is written by area.
| Stage | Typical time | What happens |
|---|---|---|
| Inspection | 1 – 3 hours | Moisture and extent checked. |
| Source repair | 1 – 7 days | Leak fixed first. |
| Remediation | 1 – 5 days | Containment, removal and cleaning. |
| Clearance | 1 – 3 days | Lab results. |
| Rebuild | 1 – 2 weeks | Drywall and paint. |
Keep doors to the containment closed and HVAC returns sealed until clearance is passed.
Professional mold remediation generally costs $10 to $25 per square foot of affected area. That puts a 100 sq ft area at about $1,000 to $2,500 and a 500 sq ft area at about $5,000 to $12,500, before rebuilding.
The EPA says areas smaller than about 10 square feet can usually be cleaned by the homeowner once the water problem is fixed. Larger areas, growth after major water damage or sewage, and suspected HVAC contamination call for an experienced contractor.
Usually only when the mold results from a covered, sudden water loss such as a burst pipe, and often only up to a separate mold limit such as $5,000 or $10,000. Mold from gradual leaks, humidity or neglect is typically excluded.
Attic mold remediation typically runs $1,000 to $4,000, depending on how much roof sheathing is affected, whether insulation has to be removed and whether ventilation needs fixing so the moisture does not return.
When mold is visible, the EPA generally does not consider sampling necessary to decide on cleanup—the growth simply needs to be removed. Testing is more useful to look for hidden growth or to confirm the area is clean before the wall is closed.
It will if the moisture source is not fixed. Remediation removes existing growth; keeping it away depends on repairing the leak, drying materials fully and controlling indoor humidity.
Not because of its color. Remediation is priced by the size of the affected area, how hard it is to reach and how much material has to come out, so black mold falls in the same $10 to $25 per square foot range as other growth. Public health guidance treats all indoor mold the same way: fix the moisture source and remove the growth, without paying to identify the species first. The cost to repair mold damage rises when drywall, insulation or subfloor has to be replaced afterward, and that rebuild is a separate line from the cleanup.
Usually, yes. Drywall, ceiling tile and insulation with visible growth are cut out and replaced, because surface cleaning does not reach growth inside the paper and gypsum. Hard surfaces such as studs and concrete can often be cleaned and dried in place. EPA guidance suggests a trained remediator for areas larger than about 10 square feet.
At about $10 to $25 per affected square foot, a 100 sq ft basement wall runs about $1,000 to $2,500 before anything is rebuilt. Garages with open studs and bare concrete often land near the low end because less material is removed. Finished basements land higher because drywall, insulation and flooring are replaced.
When the mold remediation quote touches the claim or another part of the house, start here.
Planning topics covered in the calculator and guide above.